<div class="container-fluid">
    <div class="row">
        <div class="col-md-12">
            <input class="form-control form-control-lg fa-3x" placeholder="请输入金额 ￥" id="txtMoney" autofocus />
        </div>
        <div class="col-md-12 my-3">
            <input class="form-control form-control-lg fa-3x" id="txtCapital" />
        </div>
    </div>
</div>

<script>
    //by https://github.com/michaellyu/rmb-x

    function rmb(value) {
        if (Object.prototype.toString.call(value) === '[object Number]' && value >= 0.01) {
            const numbers = ['零', '壹', '贰', '叁', '肆', '伍', '陆', '柒', '捌', '玖'];
            const leftUnits = ['元', '拾', '佰', '仟', '万', '拾', '佰', '仟', '亿', '拾', '佰', '仟', '万', '拾', '佰', '仟', '万'];
            const rightUnits = ['角', '分'];

            const fragment = [];
            const [leftValues, rightValues] = String(value)
                .split('.')
                .map(part => part.split('').map(i => i * 1));

            const leftValueLength = leftValues.length; // 整数部分位数
            const unit1 = leftValueLength - 1; // 元位
            const unit5 = leftValueLength - 5; // 万位
            const unit9 = leftValueLength - 9; // 亿位
            const unit13 = leftValueLength - 13; // 万亿位
            const unit17 = leftValueLength - 17; // 万万亿位
            const hasLeftValue = leftValueLength > 1 || leftValues[0] > 0; // 整数部分不为0
            const hasRightValue = rightValues && (rightValues[0] > 0 || rightValues[1] > 0); // 小数部分不为0
            const has678Value = leftValues[unit5 - 1] > 0 || leftValues[unit5 - 2] > 0 || leftValues[unit5 - 3] > 0; // 拾万、佰万或仟万位不为0
            const overflowIndex = leftValueLength - leftUnits.length; // 溢出位索引

            let leftUnitIndex = 0;
            for (let i = leftValueLength - 1; i >= 0; i--) {
                if (
                    (leftValues[i] > 0)
                    || (i === unit1 && hasLeftValue)
                    || (i === unit5 && has678Value)
                    || i === unit9
                    || i === unit13
                    || i === unit17
                ) { // 元、万、亿、万亿、万万亿或当前位不为0
                    fragment.unshift(leftUnits[leftUnitIndex]);
                }

                if (
                    leftValues[i] > 0
                    || (leftValues[i + 1] > 0 && i !== unit5 && i !== unit9 && i !== unit13 && i !== unit17)
                    || i <= overflowIndex
                ) { // 当前位不为0，或低一位不为0且当前位非万、亿、万亿、万万亿，或当前为溢出位
                    fragment.unshift(numbers[leftValues[i]]);
                }

                leftUnitIndex++;
            }

            if (hasRightValue) {
                // 角
                if (rightValues[0] > 0 || hasLeftValue) { // 角位不为0，或整数位不为0
                    fragment.push(numbers[rightValues[0]]);
                }
                if (rightValues[0] > 0) { // 角位不为0
                    fragment.push(rightUnits[0]);
                }
                // 分
                if (rightValues[1] > 0) {
                    fragment.push(numbers[rightValues[1]]);
                    fragment.push(rightUnits[1]);
                }
            } else { // 没有小数位
                fragment.push('整');
            }
            return fragment.join('');
        }
        return '零元整';
    }

    $('#txtMoney').on('input', function () {
        $('#txtCapital').val(rmb(Number(this.value.trim())))
    })
</script>